1. Field of the Invention
The present invention relates to curing an elastomeric article in a mold with vent passages. In particular, the present invention relates to curing a tire so a portion of elastomeric material comprising the tire is restricted from extending into one of the vent passages during the curing operation.
2. Description of the Prior Art
A mold for curing an elastomeric article, such as a tire, typically includes a cavity for shaping the tire. An inflatable bladder is located within the tire and is pressurized to press the tire against a surface of the cavity. A plurality of vent passages communicate the cavity with the exterior of the mold. The vent passages allow fluid to escape from between the tire and the surface defining the cavity. This venting of the cavity enables the tire to contact the largest possible surface area of the cavity for optimal curing.
It is known that uncured elastomeric material comprising the tire is capable of flowing into the vent passages before the elastomeric material cures to a state in which flow is inhibited. When the elastomeric material cures inside of the vent passages, the tire may have many visually unappealing projections which require trimming. Furthermore, cured elastomeric material projecting into a vent passage may tear from the tire at its base and remain in the vent passage after the tire is removed from the mold. The vent passage is blocked from communicating the cavity with the exterior of the mold. The blocked vent passage must then be cleaned before a subsequent curing operation takes place. Cleaning the vent passage is time and labor intensive which adds cost to the production of a tire.
U.S. Pat. No. 4,436,497 addresses the problem of cured elastomeric material remaining in a vent passage in a tire mold. A vent plug is provided which effectively reduces the cross sectional area of the vent passage. This reduces the thickness of the cured elastomeric material projecting from the tire into the vent passage. The vent plug also includes a chamfer located adjacent the cavity. The chamfer increases the strength of the projection near its base to prevent tearing of the projection and remaining in the vent plug. However, nothing limits how far the projection extends into the vent passage.
U.S. Pat. No. 4,812,218 discloses a tire mold having vent passages communicating a cavity with an annular fluid evacuation chamber extending around a tread ring in the mold. The chamber and vent passages are pressurized after a tire is pressed against a surface of the tread ring. Pressurizing the vent passages minimizes the amount of elastomeric material which flows into the vent passages prior to curing. However, pressurizing the vent passages in a traditional, or nonevacuated, tire mold may prove difficult at best.